[MIPS] Forbid $sp update at the end of the last bundle.

src/trusted/validator_mips/validator.cc

Index: src/trusted/validator_mips/validator.cc
diff --git a/src/trusted/validator_mips/validator.cc b/src/trusted/validator_mips/validator.cc
index 1e4d71e651258106447f6e1013b11454983db0dd..33fdfe20eebaf58cbd722b17bc23541bcd24b237 100644
--- a/src/trusted/validator_mips/validator.cc
+++ b/src/trusted/validator_mips/validator.cc
@@ -355,6 +355,12 @@ bool SfiValidator::ValidateFallthrough(const CodeSegment &segment,
 
     prev = inst;
   }
+
+  // Validate the last instruction, paired with a nop.
+  const Instruction nop(nacl_mips_dec::kNop);
+  DecodedInstruction one_past_end(segment.EndAddr(), nop, initial_decoder);

[JF, 2012/11/16 21:03:27]

Why initial_decoder here?

The ARM change does:
decode_state_.decode(nop)

[petarj, 2012/11/19 18:46:10]

Changed to nacl_mips_dec::decode(nop, decode_state_).

+  complete_success &= ApplyPatterns(prev, one_past_end, critical, out);
+
   return complete_success;
 }